FIELD
[0001] The present disclosure relates to aircraft braking systems. In particular, the disclosure
relates to systems and methods for determining brakefail conditions of aircraft brakes.
BACKGROUND
[0002] Aircraft brake systems typically employ a series of friction disks compressed together
to stop the aircraft. Some aircraft brake systems adjust the compression of the friction
disks by controlling a servo valve to adjust the pressure of a hydraulic actuator.
Other aircraft brake systems adjust the compression of the friction disks by controlling
electronic actuators. The aircraft brake systems may control the compression of the
friction disks based on a feedback loop including the received braking request and
feedback from the servo valve or actuators. Brake control systems are disclosed in
GB 2470251 and
US 2008/154470.
SUMMARY
[0003] Provided herein is a system in accordance with various embodiments for two-stage
determination of a brakefail of an aircraft brake system as claimed in claim 1.
[0004] In any of the foregoing systems, the BCU is configured to determine that the brakefail
event has occurred in response to determining that the detected pressure value is
greater than or less than the pressure command value by at least a predetermined pressure
tolerance.
[0005] In any of the foregoing systems, the BCU is further configured to determine that
the brakefail event has occurred in response to determining that the current command
value is within a predetermined current tolerance of a maximum current value or a
minimum current value.
[0006] In any of the foregoing systems, the pressure command value is received from a brake
control executive unit and is determined based on a pilot desired pressure value and
a desired pressure command value.
[0007] In any of the foregoing systems, the current command value is determined using a
feedback loop based on the pressure command value and the detected pressure value
when the brakefail event has not occurred.
[0008] In any of the foregoing systems, the current command value is determined using an
open loop based on the pressure command value when the brakefail event has occurred.
[0009] Also described is a system in accordance with various embodiments for two-stage determination
of a brakefail of an aircraft brake system. The system includes an aircraft brake
having a plurality of electronic actuators each configured to receive a current command
value, to convert the current command value into a force and to output a detected
or calculated force value. The system also includes a brake control unit (BCU) configured
to determine a force command value, convert the force command value to the current
command value and to determine whether a brakefail event has occurred based on the
force command value, the current command value and the detected or calculated force
value from each of the plurality of electronic actuators.
[0010] In any of the foregoing systems as described, the BCU is configured to determine
that an actuator fail event has occurred for an electronic actuator of the plurality
of electronic actuators in response to determining that the detected or calculated
force value for the electronic actuator is greater than or less than the force command
value by at least a predetermined force tolerance.
[0011] In any of the foregoing systems as described, the BCU is further configured to determine
that the actuator fail event has occurred for the electronic actuator in response
to determining that the current command value is within a predetermined current tolerance
of a maximum current value or a minimum current value for the electronic actuator.
[0012] In any of the foregoing systems as described, the BCU is further configured to determine
that the brakefail event has occurred in response to determining that the actuator
fail event has occurred for a predetermined number of the plurality of electronic
actuators.
[0013] In any of the foregoing systems as described, the BCU is further configured to determine
that the actuator fail event has occurred in response to determining that the detected
or calculated force value is greater than or less than the force command value by
at least the predetermined force tolerance or that the current command value is within
the predetermined current tolerance of the maximum current value or the minimum current
value for a predetermined period of time.
[0014] In any of the foregoing systems as described, the BCU is configured to determine
that the actuator fail event has stopped occurring in response to determining that
the detected or calculated force value is within the predetermined force tolerance
of the force command value and that the current command value is less than the maximum
current value minus the predetermined current tolerance and is greater than a sum
of the minimum current value and the predetermined current tolerance for the predetermined
period of time.
[0015] In any of the foregoing systems as described, the BCU is configured to determine
that the brakefail event has stopped occurring in response to determining that the
actuator fail event is occurring for less than the predetermined number of the plurality
of electronic actuators.
[0016] Also provided is a method in accordance with various embodiments for two-stage determination
of a brakefail of an aircraft brake system as claimed in claim 5.
[0017] The forgoing features and elements may be combined in various combinations without
exclusivity, unless expressly indicated herein otherwise. These features and elements
as well as the operation of the disclosed embodiments will become more apparent in
light of the following description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The subject matter of the present disclosure is particularly pointed out and distinctly
claimed in the concluding portion of the specification. A more complete understanding
of the present disclosures, however, may best be obtained by referring to the detailed
description and claims when considered in connection with the drawing figures, wherein
like numerals denote like elements.
FIG. 1 is a block diagram showing a braking system of an aircraft for implementing
a two-stage determination of a brakefail event of the braking system, in accordance
with various embodiments;
FIG. 2 is a flowchart showing a method for a two-stage determination of the brakefail
event of FIG. 1, in accordance with various embodiments;
FIG. 3 is a block diagram showing a braking system of an aircraft having an electronic
brake and for implementing a two-stage determination of a brakefail event of the braking
system, in accordance with various embodiments; and
FIG. 4 is a flowchart showing a method for a two-stage determination of the brakefail
event of FIG. 3, in accordance with various embodiments.
DETAILED DESCRIPTION
[0019] The detailed description of exemplary embodiments herein makes reference to the accompanying
drawings, which show exemplary embodiments by way of illustration and their best mode.
While these exemplary embodiments are described in sufficient detail to enable those
skilled in the art to practice the disclosures, it should be understood that other
embodiments may be realized and that logical, chemical, and mechanical changes may
be made without departing from the scope of the invention defined by the claims. Thus,
the detailed description herein is presented for purposes of illustration only and
not of limitation. For example, the steps recited in any of the method or process
descriptions may be executed in any order and are not necessarily limited to the order
presented. Furthermore, any reference to singular includes plural embodiments, and
any reference to more than one component or step may include a singular embodiment
or step. Also, any reference to attached, fixed, connected or the like may include
permanent, removable, temporary, partial, full and/or any other possible attachment
option. Additionally, any reference to without contact (or similar phrases) may also
include reduced contact or minimal contact.
[0020] Referring to FIG. 1, an aircraft brake system, or system 100, may provide a two-stage
approach for determining a brakefail condition of an aircraft hydraulic brake 106.
The system 100 includes a brake control unit (BCU) 102, a set of pilot controls 104,
the aircraft hydraulic brake 106 and a wheel assembly 107.
[0021] The aircraft hydraulic brake 106 may be a pressure-operated brake. A servo valve
117 includes an actuation mechanism that can open and/or close to some degree, allowing
more or less pressurized fluid to drive a piston and cause compression. Thus, the
servo valve 117 may receive an instruction to increase pressure to one or more friction
disks of the aircraft hydraulic brake 106. In response, the servo valve 117 may increase
the opening to allow more pressurized fluid to drive the ram, causing the friction
disks to compress. The compression of the friction disks causes deceleration of the
wheel assembly 107. This pressure may be referred to as a braking pressure. In various
embodiments, equipment other than the servo valve 117 may be used to apply pressure
to the friction disks.
[0022] The BCU 102 may include one or more processors and one or more tangible, non-transitory
memories and be capable of implementing logic. The processor can be a general purpose
processor, a digital signal processor (DSP), an application specific integrated circuit
(ASIC), a field programmable gate array (FPGA) or other programmable logic device,
discrete gate or transistor logic, discrete hardware components, or any combination
thereof.
[0023] The aircraft hydraulic brake 106 may be controlled by the pilot controls 104. For
example, the BCU 102 may receive a pilot desired pressure value 120 that corresponds
to a desired amount of braking. For example, the pilot desired pressure value 120
can be generated or altered in response to a depression of a brake pedal within a
cockpit of the aircraft. The pilot desired pressure value 120 can also be generated
or altered in response to an instruction to retract landing gear of the aircraft.
[0024] Similarly, the aircraft hydraulic brake 106 may be controlled by an antiskid/deceleration
control unit 112 that is part of a brake control algorithm unit 108. The brake control
algorithm unit 108 that controls the braking of the aircraft based on an algorithm.
The brake control algorithm unit 108 may include the antiskid/deceleration control
unit 112, a brake control executive unit 114 and a pressure control unit 116.
[0025] The antiskid/deceleration control unit 112 may receive a fixed deceleration command
value 118 from another unit of the BCU 102, a filtered wheel speed value 130 from
the wheel assembly 107 and a filtered wheel acceleration value 128 from the wheel
assembly 107. The antiskid/deceleration control unit 112 can output a desired pressure
command value 122 corresponding to a desired amount of pressure to be applied to the
aircraft hydraulic brake 106 based on the fixed deceleration command value 118, the
filtered wheel speed value 130 and the filtered wheel acceleration value 128. The
desired pressure command value may be based on an algorithm for reducing the likelihood
of the aircraft skidding and/or based on an automatic deceleration algorithm.
[0026] The brake control executive unit 114 receives both the pilot desired pressure value
120 and the desired pressure command value 122 and issues a pressure command value
124 based on the pilot desired pressure value 120 and the desired pressure command
value 122. In various embodiments, the pressure command value 124 may be equal to
the minimum value of the desired pressure command value 122 and the pilot desired
pressure value 120. The pressure command value 124 corresponds to a desired amount
of pressure to be applied to the aircraft hydraulic brake 106.
[0027] The pressure control unit 116 may receive the pressure command value 124 and may
convert the pressure command value 124 into a current command value 126. The current
command value 126 may be received by the servo valve 117 of the aircraft hydraulic
brake 106. The servo valve 117 may be designed to convert the current command value
126 into a pressure. The pressure may be applied to one or more disks of a disk brake
system of the aircraft hydraulic brake 106. The relationship between received current
of the servo valve 117 and the amount of pressure applied may generally be described
as a linear relationship between current and pressure. In various embodiments, the
pressure control unit 116 may use the above relationship to determine the current
command value 126 based on the known pressure command value 124 or may use another
algorithm for determining the current command value 126 based on the pressure command
value 124. The pressure control unit 116 may also determine the current command value
126 based on a detected pressure value 132 corresponding to a detected pressure applied
to the one or more disks of the aircraft hydraulic brake 106. In that regard, the
determination of the current command value 126 may be based on a feedback system such
that the current command value 126 is adjusted in an attempt to cause the detected
pressure value 132 to be equal to the pressure command value 124.
[0028] The aircraft hydraulic brake 106 may include a pressure sensor 109 for detecting
the pressure applied by the servo valve 117. The pressure sensor 109 may transmit
the detected pressure value 132 to the pressure control unit 116 for feedback control
of the servo valve 117.
[0029] A built-in test function unit 110 may be designed to determine whether a component
failure of the aircraft hydraulic brake 106 has occurred and, in response, generate
a brakefail value 134 using a two-stage approach. The built-in test function unit
110 may determine the brakefail value 134 based on the pressure command value 124
from the brake control executive unit 114, the current command value 126 from the
pressure control unit 116 and the detected pressure value 132 from the pressure sensor
109 of the aircraft hydraulic brake 106.
[0030] The first stage may be a fine stage and the second stage may be a course stage. The
fine stage may be based on a comparison of the pressure command value 124 to the detected
pressure value 132. For example, if the detected pressure value 132 is within a predetermined
pressure tolerance of the pressure command value 124, then the fine stage may indicate
that no brakefail has occurred. In various embodiments, the pressure tolerance may
be 200 pounds per square inch (psi, 1.38 Megapascal (MPa)).
[0031] However, events may occur in which a brakefail condition is present but the detected
pressure value 132 is still within the pressure tolerance of the pressure command
value 124. For example, a pilot may request 1,150 psi (7.929 MPa) via the pilot controls
104. The pressure sensor 109 may have failed and report that the detected pressure
value 132 is 1000 psi (6.895 MPa) regardless of the actual pressure applied by the
servo valve 117. If the pressure tolerance value is 200 psi (1.38 MPa), the first
stage of detecting the brakefail will indicate that no brakefail has occurred. In
order to compensate for such a situation, the built-in test function unit 110 may
implement the course stage of brakefail determination. The course stage may be based
on the current command value 126.
[0032] When the pressure sensor 109 is in such a fail state, the pressure control unit 116
may continue to increase the current command value 126, if the detected pressure value
is less than the pressure command value 124, in an attempt to cause the detected pressure
value 132 to rise to the pressure command value 124. Similarly, if the detected pressure
value 132 is greater than the pressure command value 124, the pressure control unit
116 may continue to reduce the current command value 126 in an attempt to cause the
detected pressure value 132 to decrease to the pressure command value 124. Eventually,
in either situation, the current command value 126 will continue to increase to a
maximum current value or decrease to a minimum current value. For example, the maximum
current value may be 30 milliamps, which may be a maximum current that may be provided
by the pressure control unit 116. Similarly, a minimum current value may be 2 milliamps,
which may be a minimum current that may be provided by the pressure control unit 116.
[0033] In order to determine whether a brakefail has occurred using the course stage, the
built-in test function unit 110 will determine whether the current command value 126
is within a predetermined current tolerance of the maximum current or the minimum
current. If the detected pressure value 132 is within the pressure tolerance of the
pressure command value 124 and the current command value 126 is at a value other than
within the current tolerance of the maximum current or minimum current for a predetermined
amount of time, then the built-in test function unit 110 may indicate that no brakefail
has occurred. Stated differently, the built-in test function unit 110 may determine
that a brakefail has occurred if the current command value 126 is within the current
tolerance of the maximum current or the minimum current for the predetermined amount
of time. This indication may be provided, for example, via the brakefail value 134.
The brakefail value 134 can be provided to the pressure control unit 116 such that
open loop pressure control can be implemented. Otherwise, the built-in test function
unit 110 may indicate that a brakefail has occurred.
[0034] Turning now to FIG. 2, a method 200 for determining whether a brakefail event has
occurred in an aircraft brake using a two-stage approach may begin at block 202. The
method 200 may be performed by a built-in test function unit similar to the built-in
test function unit 110 of FIG. 1.
[0035] In block 202, the built-in test function unit may receive a pressure command from
a brake control algorithm unit. The built-in test function unit may also receive a
detected pressure corresponding to a detected pressure of an aircraft brake.
[0036] In block 206, the built-in test function unit may determine whether the detected
pressure is within the predetermined pressure tolerance of the pressure command. For
example, the built-in test function unit may determine whether the detected pressure
is within 200 psi (1.38 MPa) of the pressure command. If not, the built-in test function
unit may declare a brakefail in block 212. In various embodiments, the built-in test
function unit may not declare the brakefail unless the difference between the detected
pressure and the pressure command remains greater than the pressure tolerance for
a predetermined amount of time, such as 2 seconds. This delay reduces the likelihood
of false brakefail alerts, for example, by allowing sufficient time for a new or changed
braking command to be implemented in the brakes.
[0037] If the detected pressure is within the pressure tolerance of the pressure command,
the built-in test function unit may receive a current command in block 208, for example,
from a pressure control unit.
[0038] In block 210, the built-in test function unit may determine whether the current command
is within a current tolerance of the maximum current or the minimum current. The current
tolerance may be a predetermined value, such as 0.1 milliamp, 0.2% of the total range
of possible current values, or the like. If the current command is not within the
current tolerance of the maximum current or the minimum current, then the process
may return to block 202 and the built-in test function unit may declare that no brakefail
has occurred. However, if the current command is within the current tolerance of the
maximum current or the minimum current, the method 200 may proceed to block 212 where
the built-in test function unit will declare a brakefail. In various embodiments,
the brakefail will not be declared unless the current command remains within the current
tolerance of the maximum current or the minimum current for a predetermined amount
of time, such as 2 seconds. This reduces the likelihood of false brakefail declarations.
[0039] After declaring a brakefail, the built-in test function unit may continue to monitor
the pressure command, the current command and the detected pressure in block 214.
If, at any point after the brakefail has been declared, the detected pressure is within
the pressure tolerance of the pressure command and the current command is at a value
other than the maximum current or minimum current plus or minus the current tolerance,
then the built-in test function unit may clear the brakefail in block 216. Otherwise,
the method 200 may return to block 212 where the brakefail is still declared. In various
embodiments, the detected pressure must be within the pressure tolerance of the pressure
command and the current command must be at a value other than the maximum current
or the minimum current plus or minus the tolerance for a predetermined amount of time,
such as two seconds, before the brakefail will be cleared. This decreases the likelihood
of a false clearing of the brakefail.
[0040] Turning now to FIG. 3, another aircraft brake system (or system) 300 may provide
a two-stage approach for determining whether a brakefail has occurred regarding an
aircraft electric brake 306. The system 300 is similar to the system 100 of FIG. 1,
and like numbered components of each system 100, 300 perform similar functions. The
system 300, however, is designed using an electric brake instead of a pressure brake.
The system 300 includes a brake control unit (BCU) 302, a set of pilot controls 304,
the aircraft electric brake 306 and a wheel assembly 307.
[0041] The BCU 302 includes a brake control algorithm unit 308 that is used to control the
aircraft electric brake 306. The BCU 302 also includes a built-in test function unit
310 for determining whether a brakefail event has occurred. In particular, the brake
control algorithm unit 308 can receive a pilot desired force value 320 from the pilot
controls 304 corresponding to a brake request by the pilot. Likewise, the brake control
executive unit 314 can receive a desired force command value 322 received from an
antiskid/deceleration control unit 312. As with the antiskid/deceleration control
unit 112 of FIG. 1, the antiskid/deceleration control unit 312 may generate the desired
force command value 322 based on a fixed deceleration command value 318, a filtered
wheel acceleration value 328 and a filtered wheel speed value 330. The brake control
executive unit 314 may output a force command value 324 that is equal to a minimum
of the pilot desired force value 320 or the desired force command value 322.
[0042] The aircraft electric brake 306 may include a plurality of electronic actuators 350
including a first electronic actuator 350A, a second electronic actuator 350B, a third
electronic actuator 350C and a fourth electronic actuator 350D. Each of the electronic
actuators 350 may apply a force to one or more disks of the aircraft electric brake
306 to decelerate angular velocity of the wheel assembly 307. The force may be determined
based on a received signal from the BCU 302. In particular, the force control unit
316 may be designed to provide a current command value 326 to each of the electronic
actuators 350 based on the force command value 324. The current command value 326
may instruct each of the electronic actuators 350 to apply a desired amount of force
to the disks. In various embodiments, the force command value 324 may be determined
for each of the electronic actuators 350 and, in further embodiments, the force control
unit 316 may determine each of the current command values 326 based on a single force
command value 324.
[0043] In various embodiments, a force sensor may be coupled to each of the electronic actuators
350 and designed to detect a force applied by each of the electronic actuators 350.
In further embodiments, logic may be implemented in the BCU 302 and/or the aircraft
electric brake 306 for calculating the force applied by each of the electronic actuators
350. The current command value 326 may also be based on a detected and/or calculated
force applied by each of the electronic actuators 350. In that regard, the current
command value 326 may be determined based on a closed loop system.
[0044] The built-in test function unit 310 may be designed to determine whether a brakefail
has occurred within the aircraft electric brake 306 based on the force command value
324, the detected/calculated force value 332 from each of the electronic actuators
350 and the current command value 326 provided to each of the electronic actuators
350. If a brakefail has been determined by the built-in test function unit 310, the
built-in test function unit 310 may report the brakefail to the brake control executive
unit 314 via a brakefail value 334. The brakefail value 334 may also be provided to
the force control unit 316 for implementation of open-loop force control.
[0045] The built-in test function unit 310 may compare the detected/calculated force value
332 from each of the electronic actuators 350 to the force command value 324. If the
detected/calculated force value 332 for each of the electronic actuators 350 is not
within a predetermined force tolerance of the force command value 324 for a predetermined
amount of time, the built-in test function unit 310 may determine that the corresponding
actuator is in an actuator fail state. The comparison of the force command value 324
to the detected/calculated force value 332 is the fine determination stage.
[0046] As with the pressure control unit 116 of FIG. 1, the force control unit 316 may continue
to increase an amount of current to any of the electronic actuators 350 in which the
force sensor and/or the calculation of force therefrom is not functioning properly.
Thus, the built-in test function unit 310 may compare the current command value 326
for each of the electronic actuators 350 to a minimum current value and a maximum
current value. If the detected/calculated force value 332 for each of the electronic
actuators 350 is within a predetermined force tolerance of the force command value
324 and the current command value 326 for any of the electronic actuators 350 is within
a current tolerance of the maximum current value or the minimum current value, the
built-in test function unit 310 may determine that the corresponding electronic actuator
is in an actuator fail state. In various embodiments, the current command value 326
should be within the current tolerance of the maximum current value or the minimum
current value for a predetermined amount of time before the electronic actuator will
be declared to be in the actuator fail state.
[0047] Because the aircraft electric brake 306 includes four separately controlled electronic
actuators 350, a desired force corresponding to the force command value 324 may be
applied to the disk brake system even if one or more of the electronic actuators 350
is in an actuator fail state. Thus, the built-in test function unit 310 may be designed
to declare a brakefail only if a predetermined number of the electronic actuators
350, such as two of the electronic actuators 350, are in an actuator fail state. However,
the built-in test function unit 310 may report any of the electronic actuators 350
that are in the actuator fail state to the brake control executive unit 314 and/or
any other unit.
[0048] Turning to FIG. 4, a method 400 for a two-stage determination of a brakefail in an
aircraft electric brake may begin at block 402. The method 400 may be performed by
a built-in test function unit such as the built-in test function unit 310 of FIG.
3. In block 402, the built-in test function unit may receive a force command along
with a detected and/or calculated force from one of a plurality of actuators.
[0049] In block 406, the built-in test function unit may determine whether the detected/calculated
force is within the force tolerance of the force command for the corresponding actuator.
If the detected force for the corresponding actuator is not within the predetermined
force tolerance of the force command, the method 400 may proceed to block 412 where
an actuator fail event may be declared for the current actuator. In various embodiments,
the method 400 will not proceed to declare an actuator fail until the difference between
the detected/calculated force and the force command is greater than the force tolerance
for a predetermined amount of time, such as between 0.5 and 3.5 seconds, or between
1 and 3 seconds, or 2 seconds. However, if the detected force is within the force
tolerance of the force command for the current actuator, the method 400 may proceed
to block 408. In block 408, the built-in test function unit may receive the current
command so that it can determine whether one or more actuator is in an actuator fail
state based on the current command.
[0050] In block 410, the built-in test function unit may compare the current command to
a maximum current value and a minimum current value. If the current command is within
a current tolerance of the maximum current or the minimum current, the built-in test
function unit may determine that the current actuator is in the actuator fail state
and proceed to block 412. In some embodiments, the method 400 will not proceed to
block 412 unless the current command is within the current tolerance of the maximum
current value or the minimum current value for a predetermined amount of time, such
as between 0.5 and 3.5 seconds, or between 1 and 3 seconds, or 2 seconds. If, on the
other hand, the current command value is not within the current tolerance of the maximum
current value or the minimum current value, then the method 400 may return to block
402.
[0051] In block 414, the built-in test function unit may determine how many of the actuators
are in the actuator fail state. If a predetermined number of actuators are in the
actuator fail state, then the method 400 may proceed to block 416. The predetermined
number of actuators may correspond to a number of actuators without which the aircraft
electric brake could not apply a maximum amount of force. If fewer than the predetermined
number of actuators are in the actuator fail state, then the method 400 may clear
the brakefail condition in block 415, if previously set, and then return to block
402. However, if the predetermined number of actuators, or more than the predetermined
number of actuators, are in the actuator fail state, then the built-in test function
unit may declare that a brakefail event has occurred in block 416 and report the brakefail
to the brake control executive unit and/or force control unit.
[0052] In block 418, the built-in test function unit may determine, for each of the actuators
in the actuator fail state, whether the detected force is within the force tolerance
of the force command and whether the current command is at a value not within the
current tolerance of the maximum current or the minimum current. If not, the method
400 may return to block 414 in case another actuator is no longer in the actuator
fail state. However, if so, the method 400 may proceed to block 420 where the actuator
fail state for the current actuator will be cleared. In various embodiments, the built-in
test function unit may ensure that these conditions are met for a predetermined period
of time, such as two seconds, prior to clearing the actuator fail state. After clearing
the actuator fail state in block 420, the method may then proceed to block 414 where
the built-in test function unit determines whether the predetermined number of actuators
are still in the actuator fail state.
[0053] Referring now to FIGS. 1 and 3, the systems 100 and 300 may control the aircraft
hydraulic brake 106 and the aircraft electric brake 306 using an open loop control
method if either has been declared to be in brakefail. As a result, the pressure control
unit 116 may only determine the current command value 126 based on the pressure command
and the force control unit 316 may only control the current command values 326 based
on the force command value 324. This tends to eliminate incorrect information received
from the aircraft hydraulic brake 106 and the aircraft electric brake 306.
[0054] Benefits, other advantages, and solutions to problems have been described herein
with regard to specific embodiments. Furthermore, the connecting lines shown in the
various figures contained herein are intended to represent exemplary functional relationships
and/or physical couplings between the various elements. It should be noted that many
alternative or additional functional relationships or physical connections may be
present in a practical system. However, the benefits, advantages, solutions to problems,
and any elements that may cause any benefit, advantage, or solution to occur or become
more pronounced are not to be construed as critical, required, or essential features
or elements of the disclosures. The scope of the disclosures is accordingly to be
limited by nothing other than the appended claims, in which reference to an element
in the singular is not intended to mean "one and only one" unless explicitly so stated,
but rather "one or more." Moreover, where a phrase similar to "at least one of A,
B, or C" is used in the claims, it is intended that the phrase be interpreted to mean
that A alone may be present in an embodiment, B alone may be present in an embodiment,
C alone may be present in an embodiment, or that any combination of the elements A,
B and C may be present in a single embodiment; for example, A and B, A and C, B and
C, or A and B and C. Different cross-hatching is used throughout the figures to denote
different parts but not necessarily to denote the same or different materials.
[0055] Systems, methods and apparatus are provided herein. In the detailed description herein,
references to "one embodiment", "an embodiment", "an example embodiment", etc., indicate
that the embodiment described may include a particular feature, structure, or characteristic,
but every embodiment may not necessarily include the particular feature, structure,
or characteristic. Moreover, such phrases are not necessarily referring to the same
embodiment. Further, when a particular feature, structure, or characteristic is described
in connection with an embodiment, it is submitted that it is within the knowledge
of one skilled in the art to affect such feature, structure, or characteristic in
connection with other embodiments whether or not explicitly described. After reading
the description, it will be apparent to one skilled in the relevant art(s) how to
implement the disclosure in alternative embodiments.
[0056] Furthermore, no element, component, or method step in the present disclosure is intended
to be dedicated to the public regardless of whether the element, component, or method
step is explicitly recited in the claims. As used herein, the terms "comprises", "comprising",
or any other variation thereof, are intended to cover a non-exclusive inclusion, such
that a process, method, article, or apparatus that comprises a list of elements does
not include only those elements but may include other elements not expressly listed
or inherent to such process, method, article, or apparatus.
1. A system for two-stage determination of a brakefail of an aircraft brake system comprising:
a wheel assembly (107)
a hydraulic aircraft brake (106) configured to receive a current command value, to
convert the current command value into a force or braking pressure and to output a
detected or calculated pressure value; and
a brake control unit BCU (102) having a deceleration control unit (112) configured
to generate a pressure command value (122) based on at least one of a fixed deceleration
command value (118), a filtered wheel acceleration value (128) taken from the wheel
assembly (107), and a filtered wheel speed value (130) taken from the wheel assembly
(107), the brake control unit BCU (102) being configured to convert the pressure command
value to the current command value and to determine whether a brakefail event has
occurred based on the pressure command value, the current command value and the detected
or calculated pressure value;
wherein the BCU is configured to determine that the brakefail event has occurred in
response to determining that the detected pressure value is greater than or less than
the command value by at least a predetermined pressure tolerance or in response to
determining that the current command value is within a predetermined current tolerance
of a maximum current value or a minimum current value;
wherein the BCU is configured to determine that the brakefail event has stopped occurring
in response to determining that the detected pressure value is within the predetermined
pressure tolerance of the pressure command value and that the current command value
is less than the maximum current value minus the predetermined current tolerance and
is greater than a sum of the minimum current value and the predetermined current tolerance
for the predetermined period of time.
2. The system of claim 1, wherein the BCU is further configured to determine that the
brakefail event has occurred in response to determining that the detected pressure
value is greater than or less than the command value by at least the predetermined
pressure tolerance or that the current command value is within the predetermined current
tolerance of the maximum current value or the minimum current value for a predetermined
period of time.
3. The system of any preceding claim, wherein the command value is received from a brake
control executive unit (114) and is determined based on a pilot desired pressure value
(120) and a desired command value (122).
4. The system of any preceding claim, wherein the current command value is determined
using a feedback loop based on the pressure command value and the detected pressure
value when the brakefail event has not occurred; and preferably wherein the current
command value is determined using an open loop based on the command value when the
brakefail event has occurred.
5. A method for two-stage determination of a brakefail of an aircraft brake system comprising:
generating, by a deceleration control unit (112, 312) a pressure command value based
on at least one of a fixed deceleration command value (118, 318), a filtered wheel
acceleration value (128, 328) taken from a wheel assembly (107, 307), and a filtered
wheel speed value (130, 330) taken from the wheel assembly (107, 307).
converting, by a brake control unit, BCU, the pressure command value to a current
command value;
receiving, by the BCU, a detected or calculated pressure value; and
determining, by the BCU, whether a brakefail event has occurred based on the pressure
command value, the current command value and the detected or calculated pressure value;
determining, by the BCU, that the brakefail event has occurred in response to determining
that the detected or calculated pressure value is greater than or less than the pressure
command value by at least a predetermined pressure tolerance or that the current command
value is within a predetermined current tolerance of a maximum current value or a
minimum current value for a predetermined period of time;
determining, by the BCU, that the brakefail event has occurred in response to determining
that the detected pressure value is greater than or less than the command value by
at least a predetermined pressure tolerance or that the brakefail event has occurred
in response to determining that the current command value is within a predetermined
current tolerance of a maximum current value or a minimum current value; and
determining, by the BCU, that the brakefail event has stopped occurring in response
to determining that the detected pressure value is within the predetermined pressure
tolerance of the pressure command value and that the current command value is less
than the maximum current value minus the predetermined current tolerance and is greater
than a sum of the minimum current value and the predetermined current tolerance for
the predetermined period of time.